This invention relates to the field of disk drives used with computer systems for the storage of information, and more particularly to a method and apparatus which provides for the loading/unloading of a magnetic transducer from an associated storage medium, and the further locking of a head carriage mechanism at a selected position.
With the increased use of computers, and in particular microprocessors fabricated as integrated circuits, there has been a growing demand for devices which provide for the permanent storage of information for use therewith. In the past, there has been wide use of a magnetic medium comprised of a flexible magnetic disc, generally referred to as a floppy disk. While such a medium does provide for the permanent storage of information, both significantly improved amounts of storage as well as decreased access times have been made possible through the use of a rigid disk medium rotating at a relative high rate of speed. Broadly speaking, such a rigid disk storage apparatus is typically comprised of one or more rigid disks coated with a material having selected magnetic properties, permanently mounted in a sealed enclosure containing not only the rigid disks, but also the magnetic transducers to effect the transfer of information onto and off of the surface of the rigid disks. In normal operation, the magnetic transducers "ride" or "fly" above the surface of the rigid disk on a thin layer of air created by the rotation of the rigid disk. The magnetic transducers are consequently only in contact with the surface of the rigid disk when the rigid disk is not rotating at the desired operational speed, i.e., when the rigid disk is either turned off, or is in a transitional phase of either coming up to speed in response to being turned on, or is slowing down subsequent to being turned off. With continual refinements in the associated technology, the price and physical size of rigid disk storage devices has steadily decreased, with a corresponding increase in storage capacity and reliability. There has consequently been a growing trend toward the increased use of rigid disk media for the permanent storage of information, particularly in connection with microprocessor devices.
While the rigid disk storage devices have provided an attractive solution for the permanent storage of large amounts of information, there has nevertheless been a number of long standing problems associated with the use thereof. In particular, as the magnetic transducers associated therewith are in contact with the surface of the rigid disk medium when the apparatus is first turned on, they consequently present a significant resistance to the rotation of the rigid disk. This resistance continues until the rotational speed of the rigid disk is sufficient to generate the necessary air foil on which the magnetic transducers "fly" above the surface of the rigid disk. In designs of rigid disk units employing multiple rigid disks, there is typically a magnetic transducer associated with each side of each disk. This presents a number of undersirable situations. In particular, the presence of the magnetic transducers on the surfaces of the rigid disk media results in a requirement of a significantly greater force to rotate the rigid disk media. Once the magnetic transducers are no longer in contact with the surface of the rigid disk, the necessary force to rotate the rigid disks is significantly reduced. The requirement for greater starting torque necessarily results in greater power required by the rigid disk to reach the desired operational speed.
However, while reduced starting power requirements is an important consideration, particularly with respect to portable devices employing rigid disk storage devices which operate from a battery supply, of more significance is the undesirable abrasive contact which takes place between each surface of the rigid disk and the associated magnetic transducer during both the start up and shut down phases. Such abrasive contact is clearly undesirable, as such not only could result in damage to the surface of the rigid disk, and consequent loss of information stored thereon, but also results in undesirable wear of the magnetic transducers.
While the foregoing illustrates one situation in which undesirable contact is made with the surface of the rigid disk, there are yet other ways, particularly with respect to the typical mechanical relationship which exists between the magnetic transducers and the rigid disk media. Thus, where the rigid disk and the magnetic transducers are incorporated into a hard disk drive module that is removable from a microcomputer system for transport or other handling of the module, the transducers and the rigid disk are particularly vulnerable to damage as a result of motion and contact between the transducers and the surfaces of the rigid disk as the module is repeatedly shaken and jarred.
In a rigid disk storage device, the associated magnetic transducer is typically mounted at one end of a cantilevered positioning arm, in such a fashion that the magnetic transducer may be positioned at selected radial positions across the surface of the rigid disk by the radial movement of the cantilevered positioning arm. While such an arrangement does provide the necessary radial positioning function, movement of the magnetic transducer in a direction perpendicular to the surface of the rigid disk may occur in response to unexpected physical movement of the rigid disk enclosure. Such perpendicular motion may cause the magnetic transducer to strike the surface of the rigid disk, resulting in damage to either the magnetic transducer, the surface of the rigid disk, or both.
In addition thereto, uncontrolled motion of the magnetic transducer may occur across the surface of the rigid disk in a radial fashion when the rigid disk apparatus is in a power down state. As the positioning motor employed to position the magnetic transducer with respect to the surface of the rigid disk is permanently coupled to the magnetic transducers through the cantilevered positioning arm, the operational characteristics of the head positioning motor in a power down status will in part determine potential movement characteristics of the heads across the surface of the rigid disk. In the past, stepper motors have been widely used to effect the required positioning of the magnetic transducers. As stepper motors typically have a residual cogging torque in a power down state which tends to oppose the rotation of the shaft thereof, such cogging torque acts to inhibit motion of the magnetic transducers across the surface of a rigid disk to a limited degree. In this regard, it is to be understood that such residual cogging torque is typically not sufficient to insure the complete absence of the undesirable radial motion. However, with increasing storage densities of rigid disks, the distance between adjacent tracks on the surface of the rigid disks has steadily decreased, to the point that stepper motors frequently do not provide sufficient resolution in positioning accuracy. Consequently, different types of positioning motors are now being used, e.g., Voice Coil and D.C. motors. Unfortunately, the types of motors typically used in newer designs do not provide a residual cogging torque in the power down state. Consequently, the possibility for undesired radial motion of the magnetic transducers is significantly greater in designs employing such motors.
There have been a number of approaches taken in the past to reduce the risk of damage from the foregoing discussed factors. With respect to the rigid disk media itself, improved materials used in the manufacture thereof have resulted in rigid disk surfaces which are less susceptible to damage resulting from either an undersirable direct or abrasive contact with the magnetic transducers. In a similar fashion, improvements in the design of the magnetic transducers have likewise improved not only the ruggedness of the transducers, but have likewise reduced the possibility of damage to the rigid disk media. In this regard, it is to be understood that such improvements have operated to only reduce the risks of damage, rather than eliminate it completely.
In another approach to reduce the risk of damage, prior to removing power from the rigid disk apparatus the magnetic transducers are first positioned over an area on the rigid disk which is not used for the storage of information, e.g., the inner perimeter of the rigid disk. As a consequence thereof, contact between the magnetic transducers and the surface of the rigid disk is restricted to the surface of the rigid disk where information is not stored. While such an approach does offer some degree of reduction in the risk of damage to information stored on the rigid disk, a number of undesirable aspects are necessarily associated with this technique. In particular, a portion of the surface of the rigid disk is required, thereby reducing the surface available for the storage of information. In addition, a risk of damage to the magnetic transducer still exists. In addition, there is typically not a provision to restrict the radial motion of the magnetic transducers across the surface of the disk during the power down state. Consequently, undesirable mechanical shock or vibration could result in movement of the magnetic transducers to an area on the surface of the rigid disk used for the storage of information.
Another technique employed in the past involves the physical lifting and subsequent holding of the magnetic transducers away from the surface of the rigid disk. This process is referred to as "unloading" the magnetic transducers. Thereafter, the magnetic transducers may be lowered toward the surface of the rigid disk. This process if referred to as "loading" the magnetic transducers. The loading and unloading of the magnetic transducers is typically performed by an associated mechanism.
In the past, loading and unloading of magnetic transducers has been typically accomplished through geometric design characteristics of the cantilevered beam to which the magnetic heads are attached, in conjunction with a statically positioned separating element. The magnetic transducers are unloaded in response to being positioned radially outward past a selected peripheral point. In a similar fashion, the magnetic transducers may be loaded by being positioned radially inward past the selected peripheral point. While such approach does provide for the loading and unloading of the magnetic transducers, such a design typically requires a longer head carriage stroke, and must incorporate a separate mechanism to prevent radial motion of the head carriage assembly.
With increased emphasis on portability of microprocessor based devices, and the use of rigid disks as storage devices in connection therewith, the aforedescribed conditions become even more significant.
In addition to the foregoing, advances in the technology relating to storage media are expected to likewise require either a non-contacting or a closely controlled contacting relationship between the storage medium and associated transducers.
There is consequently a significant need for a method and apparatus which provides for the unloading of magnetic transducers from an associated storage media, as well as a means to restrict undesirable radial motion of the magnetic transducers across the surface thereof.